In general, during a manufacturing process of a semiconductor device, fine patterns are formed by using photolithography. During the formation of the fine patterns, several substrates, referred to as transfer masks (e.g., photomasks), are used. Such transfer masks are fabricated by forming fine patterns having metal thin films and the like on a transparent glass substrate. Photolithography is also used in the manufacturing process of the transfer mask.
As a kind of the transfer mask, a halftone phase shift mask is known in addition to a binary mask with a light-shielding film pattern which is made of chromium-based materials formed on a transparent substrate.
This halftone phase shift mask further includes a light-shielding film pattern (e.g., a light-shielding band) made mainly of chromium at an outer circumference of a transfer region on a semi-transmitting film pattern. Although being repeatedly used as a reticle of a stepper, the halftone phase shift mask strictly shields light incident on portions which should not be exposed, by the light-shielding film pattern (for example, See Japanese laid-upon Patent Publication No. 2005-92241).
Such halftone phase shift masks are fabricated through a series of processes as follows: writing a desired pattern on a first resist film formed on a mask blank, developing the first resist film to form a resist pattern, etching a light-shielding film using the resist pattern to form a light-shielding film pattern, etching a semi-transmitting film using the light-shielding film pattern to form a semi-transmitting film pattern, and stripping the residual first resist film. Afterwards, a series of subsequent processes are performed as follows: applying a second resist film, writing a desired pattern on the second resist film, developing the second resist film to form a resist pattern, etching a light-shielding film using the resist pattern to form a light-shielding film pattern (e.g., a light-shielding band), and stripping the residual second resist film.
As described above, during the manufacturing process of a halftone phase shift mask, it is necessary to repeat the processes of applying, writing, developing, and stripping of a resist two times in order to form the light-shielding band. Therefore, the repetitive processes are time-consuming and labor intensive increasing cost. Specifically, if the second resist film is exposed using an electron beam writing apparatus, fabrication time is dramatically increased thereby affecting the lead time in a production line.
Moreover, to follow a recent pattern of miniaturization, high fabrication accuracy of the second resist film is highly recommended. Therefore, it is necessary to upgrade alignment accuracy to the exposed portions. The manufacturing process, however, does not fully satisfy the abovementioned accuracy requirements.
Such problem occurs during not only the manufacture of the halftone phase shift mask with the light-shielding band but also the manufacture of a 3-dimensional mask with different fabrication depths, such as a patch of a tri-tone phase shift mask or an enhancer mask.